42 CFR §406.50

1. (a)Hospital insurance benefit payments may not be made for services furnished to an alien in any month in which his or her monthly social security benefits are suspended (or would be suspended if he or she were entitled to those benefits) because the alien remains outside the United States for more than 6 months.
2. (b)Benefits will be payable beginning with services furnished in the first full calendar month the alien is back in the United States.